The new analysis is published in the journal Circulation Heart Failure.

Coffee and Heart Failure Risk: Study Details

Mittleman's team analyzed the results of five previously published studies that looked at coffee intake and heart failure.

Four studies were done in Sweden. The fifth was done in Finland. Mittleman's research group was involved in three of the studies.

The people in the studies may have drank both caffeinated and decaf, Mittleman says. However, in Sweden and Finland, most coffee is caffeinated, he says.

In all, the researchers found more than 6,500 heart failure reports in more than 140,000 people. The follow-up time varied from study to study. It ranged from about eight to 35 years.

The researchers looked at the coffee-drinking habits of all the men and women.

Those who drank three or four servings a day had the best protection from heart failure, Mittleman says. Drinking that amount, compared to not drinking, reduced heart failure risk by 11%.

However, Mittleman says, those four servings are European style and must be translated to typically larger U.S. serving sizes.

In the countries involved in the studies, he says, "a serving size might be like 4-5 ounces."

That is about half or less than what is served in popular U.S. coffee chains, Mittleman says. For instance, at one chain, a short is 8 ounces, a tall 12, and a grande is 16 ounces.

Three or four European servings would be equivalent to about two U.S. servings, or up to about two 10-ounce cups, he says.

As coffee intake increases, the benefit declines, Mittleman found. "When you get up to five or six U.S. servings a day, we seem to see there is no further benefit and perhaps you are getting into a territory with increased risk," he says.

"From these data, with respect to heart failure risk, stopping at about six [cups, U.S. style] would be wise," he says."Once you get beyond about 50 ounces a day, or five 10-ounce cups, you might be getting into harm territory."

Coffee and Heart Failure Risk Reduction, Explained?

The health benefits linked with coffee aren't fully understood, Mittleman says. He suspects the reduced heart failure risk is due to coffee's seeming ability to reduce the risk of type 2 diabetes.

Coffee Drinking and Heart Health: Second Opinion

The study is potentially good news, especially for people at risk of heart failure, says cardiologist Arthur Klatsky, MD, adjunct investigator at the Kaiser Permanente Northern California Division of Research and a senior consultant in cardiology for Kaiser.

He reviewed the findings.

"The chief practical application of this study is, people with heart disease at risk of heart failure should not be advised to totally abstain from coffee if they drink moderately," Klatsky says.

Klatsky defines "moderately" as not more than four cups a day.

However, he stresses that "the study does not prove benefit [of coffee in reducing heart failure risk]."